This present application relates generally to systems and apparatus for modifying turbine wheel holes. More specifically, but not by way of limitation, the present application relates to systems and apparatus for enhancing turbine performance by reducing or plugging turbine wheel holes.
Turbine wheel holes are common in the turbine industry. Generally, these holes are defined through turbine wheels, which connect the turbine buckets or blades to the rotor. Turbine wheel holes allow the passage of a secondary flow of working fluid through the turbine wheels. This flow path may be provided for several reasons. First, for example, turbine wheel holes allow the leakage of secondary flow through the turbine wheel so to prevent reentry of the working fluid back into the primary flow path, which may cause inefficient flow patterns. In addition, wheel holes may be used to reduce the pressure drop across a turbine stage or to reduce axial pressure on the turbine wheel, which under certain operating conditions may be preferred or necessary. Generally, turbine wheel holes may measure approximately 0.5 to 3.0 inches in diameter and, when present, a turbine wheel may have approximately 3 to 15 wheel holes defined through its axial thickness.
Often, it becomes desirable to cover, plug, block or partially block turbine wheel holes. Depending on certain operating conditions, it may be preferable to completely block turbine wheel holes so that no flow is allowed to pass therethrough, or it may be preferable to partially block turbine wheel holes, i.e., reducing the diameter of the wheel hole, so that a decreased amount of flow is allowed to pass therethrough. The reasons for blocking or reducing turbine wheel holes may be several. Many times, plugging the turbine wheel holes is done during the process of refurbishing older turbine engines. The plugging is done to improve the efficiency of the engine. However, processes, systems and/or apparatus currently used for plugging turbine wheel holes are overly complex, time consuming and expensive. Thus, there is a need for improved methods, systems and/or apparatus for plugging turbine wheel holes in an efficient and cost effective manner.